As well known to those skilled in the art, there have been disclosed several kinds of water sampling devices to sample water from such sources as wells, ponds, rivers, lakes, the sea, etc, at a given depth. As a prior step to analyze a pollution level, bacteria, organisms, compositions, etc. of the water sampled by the water sampling devices or other means, the sampled water is filtered through a porous filter paper. Subsequently, the served filter paper and the filtered water are collected at the same time. As such, there has been proposed a filtering device capable of simultaneously collecting the served filter paper and the filtered water.
As shown in FIG. 1, the conventional filtering device for both pressuring and decompressing comprises a funnel-shaped filtering unit 1 and a flask 10. The sampled water is filtered through the filter paper 4 of the funnel-shaped filtering unit 1 and the filtered water flows into the flask 10.
Said funnel-shaped filtering unit 1 comprises an influx container 2, a seat 6, a feeding pipe 7, and a plug 9 which is holed through. The influx container 2 is cup-shaped without the bottom. A flange 3 is provided around an outer edge of the open bottom of the influx container 2. The sampled water for analyzing is fed into an upper portion of the funnel-shaped filtering unit 1, such that the sampled water flows downward. The seat 6 is holed through. A mesh 5 is placed on the seat 6 to support the filter paper 4, and then the flange 3 of the influx container 2 is seated on the seat 6. A feeding pipe 7 downwardly extends from the seating part 6. The feeding pipe 7 and the seat 6 may be a single body. Alternatively, the feeding pipe 7 and the seat 6 may be assembled when they are used. The plug 9 is holed through along its center and the feeding pipe 7 is fitted into the through hole of the plug 9.
Said flask 10 is provided at its upper portion with a drain port 11 through which air or the filtered water passes. The plug 9 is fitted into the mouth 12 of the flask 10. A tube (not shown) may be connected to the drain port 11 to drain the surplus filtered water from the flask 10. Further, a vacuum pump (not shown) may be connected to the tube.
In such said conventional device, the sampled water fed into the influx container 2 is filtered through the filter paper 4 which is interposed between the flange 3 of the influx container 2 and the seat 6, and almost all of the filtered water which is filtered through the filter paper 4 flows into the flask 10 via the feeding pipe 7 which extends downwardly from the seat 6.
So it is possible to collect the served filter paper 4 and the filtered water from the conventional device simultaneously. However, in order to transfer the filtered water in the flask 10 to the filtered water container 15, the plug 9 of the funnel-shaped filtering unit 1 must be detached from the flask 10 and then the filtered water in the flask 10 must be poured into the filtered water container 15. So it is inconvenient to use the conventional device and the filtered water may be polluted during the transferring step of the conventional device.
Furthermore, because the conventional device is designed such that the sampled water flows downwards due to the gravity, it takes a considerably long time to filter the sampled water through the filter paper 4. And the filtered water may be not fed into the flask 10 when the filter paper 4 is clogged with the impurities of the sampled water. In order to solve the problems, the vacuum pump is connected to the drain port 11 of the flask 10. When the vacuum pump is operated to generate negative pressure in the flask 10, the sampled water may be filtered through the filter paper 4 more rapidly. However, the filtered water may be fed into the flask 10 above the drain port 11 and then the filtered water may flow into the vacuum pump. Thus, in order to prevent the filtered water from feeding into the flask 10 above the drain port 11, it is necessary to observe whether the filtered water is fed in the filtered water container above the drain port 11 or not and transfer the filtered water in the flask 10 to another container before the filtered water is fed above the drain port 11.
So it is inconvenient and troublesome to use the conventional device.